Great War truck Posted September 9, 2012 Author Share Posted September 9, 2012 Not a lot going on at the moment where we have all been diverted into other “pressing” things! However, some engine bits have been cleaned and painted ready for re-assembly! Quote Link to comment Share on other sites More sharing options...
Minesweeper Posted September 17, 2012 Share Posted September 17, 2012 Chased the Company asked to provide the Cylinder Liners today as they seem to be taking a long time over them - but I think that probably due to a misunderstanding, they had not started to process them yet! Anyhow, the order confirmed (again) today and delivery now promised within another four to five weeks........... We really do want to get on with the engine now. Tony Quote Link to comment Share on other sites More sharing options...
nz2 Posted September 17, 2012 Share Posted September 17, 2012 I notice you are painting the engine parts green. Will this be the final colour? The Thornycroft M4 engines I have show grey paint about them and some red painted areas. The red could be a latter addition or else post war production. About the chassis' frames and wheels also is grey paint. Do you have samples kept of the original paint? It would be interesting to piece together when any colour change occurred. Doug Quote Link to comment Share on other sites More sharing options...
Old Bill Posted September 17, 2012 Share Posted September 17, 2012 Hi Doug. I have a suspicion that Thornycrofts painted their engines grey as standard but neither of ours has any sign of top coat paint on it. I could easily believe that they painted everything army green for simplicity during the war years. I also think it likely that when a lorry went through shops, the engine was painted green, even if it had been grey from new. It makes our life easier to paint it that colour anyway! When Dad cleaned the flywheel back, the back of it had a very heavy coat of primer of a grey colour which took some shifting. There was no sign of top-coat however. When we first got the chassis in the 1980's it had a patch of black paint on the side. This was rubbed back with brasso to reveal the original khaki-brown. We had bought paint which Richard had mixed for the Imperial War Museum gun-lorry and it was a match so we have continued with the colour across the fleet. This may not be the correct shade for the US Army FWD but we have no evidence for that one at all. Tim has a photo of paint being mixed in the field in a barrel using a plank to stir with and shovels full of pigment being fed in. I think it likely that any shade of khaki-brown that we produce will have had at least one vehicle in service carrying the same shade! Steve Quote Link to comment Share on other sites More sharing options...
Great War truck Posted September 28, 2012 Author Share Posted September 28, 2012 Tony started to cut the flanges on the Exhaust Valve Caps, to leave the tabs remaining which will hold them in place. Rotary table next to finish the job. The smaller section of the flange between the two cuts seen in the picture will be the tab with the larger section of the flange still to come off. Quote Link to comment Share on other sites More sharing options...
Roy Larkin Posted September 29, 2012 Share Posted September 29, 2012 About the chassis' frames and wheels also is grey paint. Do you have samples kept of the original paint? It would be interesting to piece together when any colour change occurred. Doug Late 1914 to early 1915 seems the most likely timeframe for the change of colour from grey to khaki/brown/green. The buses carried tins of grey paint when they left Grove Park in October 1914. Ambulances were originally white but were repainted khaki/brown/green very quickly in late 1914. So, even while grey paint was still being used in October 1914, the khaki/brown/green colour was also being used at the same time. Late 1914 to Spring 1915 seems to be the period when the colour change took place depending on how busy each company was and availability of paint. The actual colour they were changed to depended, it seems, on availability of correct quantities of pigment, mood of the mixer, amount of mud and dirt accidentally added to the mix, whether mixed commercially at home or in drums in France etc. My guess is that if it was possible to paint 10 lorries from 1 drum of paint then those were the only 10 of that exact colour. Quote Link to comment Share on other sites More sharing options...
Great War truck Posted September 29, 2012 Author Share Posted September 29, 2012 Here are the first two of four inlet valve cap retainers taken to the same stage as the exhaust valve cap retainers. Like the exhaust valve caps, the bulk of the flanges remain to be machined away. It should be possible to do all eight with the same set-up Quote Link to comment Share on other sites More sharing options...
Great War truck Posted October 2, 2012 Author Share Posted October 2, 2012 (edited) With the flanges now all marked out on the Inlet and Exhaust Valve caps, the final job to do on them is to machine away the superfluous part of the flanges – to just leave the locking tabs. Started with one of the Inlet Valve Caps and this was set up on a Rotary Table in the Milling Machine – using a “Clock Gauge” to ensure centricity. The top flange was worked on first of all with the unwanted parts of the flange each side of the locking tab gradually milled away. This was then taken off the mill so that it could be inverted for the other side to be similarly dealt with. These three pictures show the bottom of cap being machined as before – after it was inverted on the milling table – and the completed item. The first picture here shows the two parts of the Valve Cap temporarily screwed together and the second picture shows the base of the assembly alongside its final position on the cylinder head. This indicates clearly how the bottom of the assembly drops into the hole in the cylinder head and then has to revolved through 90 degrees to lock in. These two pictures show the parts in their final positions – the cylinder is still rather dirty and needs to be thoroughly cleaned! Edited October 2, 2012 by Great War truck Quote Link to comment Share on other sites More sharing options...
42 chevy Posted October 2, 2012 Share Posted October 2, 2012 I am interested to know what keeps the cap from turning (loosening up) in the recess. John G Quote Link to comment Share on other sites More sharing options...
Minesweeper Posted October 3, 2012 Share Posted October 3, 2012 (edited) I am interested to know what keeps the cap from turning (loosening up) in the recess. John G Simple "stop plates" are screwed into the top of the cylinder blocks between the "dogs". These were missing on the engine when we got it but they are just pieces of steel plate and can be easily replicated. You can see one of the threaded holes (the smaller one) in the previous pictures to hold them down. Tony Edited October 3, 2012 by Minesweeper Quote Link to comment Share on other sites More sharing options...
42 chevy Posted October 3, 2012 Share Posted October 3, 2012 O.K. now I understand, thanks for the reply. As always, superb workmanship on the project. John G Quote Link to comment Share on other sites More sharing options...
Old Bill Posted October 3, 2012 Share Posted October 3, 2012 I am interested to know what keeps the cap from turning (loosening up) in the recess. John G When you look down the port, you can actually see two seats. The lower one is for the valve but the upper has a disc on top. The disc has a tapped hole in the centre for the spark plug and is pushed onto the seat by the threaded sleeve screwed down hard against it. The bayonet sleeve is just a way of providing a thread for the clamping sleeve. Screwed up tight, it shouldn't come undone but, as Father says, there is a steel strip screwed to the top of the block between the ports with the ends against the hex at the top of the sleeve. Goodness knows why Thornycrofts developed such a complicated arrangement! All of the other lorries we have had contact with just have a large tapped hole in the top of the block for a screw-in plug. Steve Quote Link to comment Share on other sites More sharing options...
mattinker Posted October 4, 2012 Share Posted October 4, 2012 (edited) Hi. it maybe to do with it being a fixed head engine, a thread failure could lead to replacing cylinders and pistons, where as on the other engines, the head alone could be changed. It dose seem strange though! Regards, Matthew Edited October 4, 2012 by mattinker spelling Quote Link to comment Share on other sites More sharing options...
Minesweeper Posted October 4, 2012 Share Posted October 4, 2012 Hi. it maybe to do with it being a fixed head engine, a thread failure could lead to replacing cylinders and pistons, where as on the other engines, the head alone could be changed. It dose seem strange though! Regards, Matthew Yes - that does seem logical, Matthew - if you look again at the pictures towards the bottom of page 14 of this thread, then it does stand up! All of these parts on the Thorny are either cast iron or steel - whilst on the Dennis which has a much more simple arrangement, the caps are made of bronze - so no rusting problem with them! Tony Quote Link to comment Share on other sites More sharing options...
Asciidv Posted October 4, 2012 Share Posted October 4, 2012 I am sure if I scroll back through these pages I would find the answer, but I am still going to ask a silly question.... I am sure that I must have missed something but I am only a casual reader to this thread as you are not working on a great engine like the White and Poppe in the Dennis! What now goes over the top of this part (the threaded bit with the hex ) to seal the hole up? Barry. Quote Link to comment Share on other sites More sharing options...
Old Bill Posted October 4, 2012 Share Posted October 4, 2012 What now goes over the top of this part (the threaded bit with the hex ) to seal the hole up? Barry. Now you are challenging my powers of descriptive English! Right. The valve sits on a nomal seat, stem downwards. Above it is the combustion chamber with the port sideways into the bore. Immediately above the valve head is another seat, just like that of the valve but a bit bigger. On top of that sits an iron disc with a lapped-in face to seal against its seat. In the middle of the disc is the tapped hole for the spark plug. Once those are in, the bayonet sleeve is dropped in on top and rotated to lock it. This has a big tapped hole in the centre into which is screwed another sleeve, this time with a hexagon end. That is screwed down with a tube spanner until it touches the spark plug disc. When screwed up tight, it holds the disc down against its seat but has the spark plug up the centre. Does that help? Perhaps we should get Father to lay all the bits out in sequence for another photo? Steve Quote Link to comment Share on other sites More sharing options...
42 chevy Posted October 4, 2012 Share Posted October 4, 2012 Steve; I think that would be helpful, we always like pictures. thanks John G Quote Link to comment Share on other sites More sharing options...
Great War truck Posted October 5, 2012 Author Share Posted October 5, 2012 Here is the sequence of pictures that John G would like to see! The first one shows the top of the cylinder and the combustion chamber before a quick clean with a rotary wire brush – the second one after this cleaning and now the two seats that Steve described in his note above are really apparent. The third picture shows the best one of the original valves – all the valves are beyond their “sell-by” date and will have to be replaced The first picture shows the Valve being dropped in – but it is so badly corroded, it will not drop down easily to its bottom seating and it has not been forced. So it is in just half way. For the purpose of this photographic sequence, imagine the valve has dropped right down to its seating. The next item to drop in is the iron disc with a tapped hole in the middle to take the Spark Plug. This is bigger in diameter than the valve head so that it drops down on the upper of the two seats. Quote Link to comment Share on other sites More sharing options...
Great War truck Posted October 5, 2012 Author Share Posted October 5, 2012 (edited) The iron disc with the spark plug thread in must now be firmly fixed down. The first item to go in is the “dog” or bayonet sleeve – you can see how it drops in and then twisted through 90 degrees to secure it. The next item to go in is the hollow sleeve – threaded 2” x 11tpi. When this is screwed down tight, the bottom of this hollow sleeve bears down on the spark-plug iron disc and holds it securely in position. The first two pictures shows the hollow sleeve screwed down tight to secure the iron disc. The third picture shows the threaded section sitting on the iron disc out of the engine just so that you can see how it holds it. The valves and iron discs are going to have to be lapped in again because of the rust and corrosion. The new valves have not yet been ordered. Edited October 5, 2012 by Great War truck Quote Link to comment Share on other sites More sharing options...
42 chevy Posted October 6, 2012 Share Posted October 6, 2012 (edited) Much appreciated, a very interesting setup. If I understand this correctly, the combustion actually takes place over the valve and not the piston in that off center area away from the piston? I would think this would inefficient but I am sure there was a good reason. I know on "modern" flat head engine the spark plug is over the valve, however, the piston is in the same "chamber" for combustion. I think I explained that correctly. If you had not posted the pictures I would have been lost. Going back to page 14 of this thread, and looking at the engine pictures it now all makes sense. Again , superb workmanship and I always look forward to the updates . John G Edited October 6, 2012 by 42 chevy Quote Link to comment Share on other sites More sharing options...
Old Bill Posted October 6, 2012 Share Posted October 6, 2012 The combustion will certainly start over the valve but the flame front will propagate across the top of the piston towards the exhaust valve on the other side. A Tee-head engine does give a very nice mechanical layout but it is very hard to get a compression ratio of much more than 4:1. This is fine for the early fuels but overhead valves allow a much better combustion chamber shape with higher ratios. Fortunately for us, ultimate performance is not an issue! Steve :-) Quote Link to comment Share on other sites More sharing options...
Great War truck Posted October 7, 2012 Author Share Posted October 7, 2012 Tony had some time yesterday so returned to the Engine Blocks to clean them – they had rusted up slightly again following the last wire-brushing, a month or two ago! Turned first of all to the valve seatings and found that after all the rust and other crud had been removed, one of the exhaust valve seats is in very poor condition and will need some significant work to get it right again. This is the lower of the two seatings visible in the first two photos. The third photo shows the advance again of the devil “rust” since the last wire brushing. After a successful but tedious wire brushing, the cylinders were washed down first of all with paraffin – dried off and then washed down again with a cellulose thinner. They were then given a coat of Bonda Primer – which is cellulose based to stop a repeat of the rusting. All the missing or damaged studs were replaced at this stage, too with ones that were previously made and were waiting to be fitted. Quote Link to comment Share on other sites More sharing options...
Kufra Kiwi Posted October 8, 2012 Share Posted October 8, 2012 That block needs a good soaking in 6:1 mollasses for 3 weeks - gets in all the nooks and crannies. Quote Link to comment Share on other sites More sharing options...
Barney Posted October 9, 2012 Share Posted October 9, 2012 When fitting new valve guides to a cylinder head it is common practice to regrind the valve seats. I was always surprised as to how far out of line the old seat was in relation to the new guide and assumed this was caused by the rockers pushing the valve to one side. Although a side valve engine tappet has a direct upward push on the valve stem I still found that sometimes the seats would be out of line. I always preferred to regrind the valves and seats even if new guides were not necessary as it was far easier and less arm aching to give the seats a quick rub-in with fine paste rather than bashing away for ages with course and then fine pastes. One point about regrinding seats is to make sure that they do not end up too wide as this causes burning of the seat. Wide seats would be reduced by topping off with a low angle stone to leave a seat about 1/8” wide. Really bad seats would require the head to be machined and an insert fitted. Normally cast iron heads were the worst effected by excessive burning or wear; alloy heads, which had inserts from new, were not usually a problem although occasionally an insert would work loose. Keep up the good work. John Quote Link to comment Share on other sites More sharing options...
Old Bill Posted October 9, 2012 Share Posted October 9, 2012 Hi John. Thanks for that. How do you grind in a valve seat? What tools do I need? I have only ever lapped valves in using paste but this seat looks like a bigger job than that! Steve Quote Link to comment Share on other sites More sharing options...
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